An electric power steering (EPS) system may be operated in various control modes for variety of steering functions and applications. For example, during typical operation of an EPS in a vehicle, the EPS may operate in torque control mode. Additionally, during autonomous driving, or automatic parking or any other such autonomous operations, the EPS may be operated in position control mode. Additionally, during controlled handwheel return operations of the vehicle, the EPS may operate in velocity control mode. In one or more examples, the torque control mode is further classified into two sub-methods. First, an assist-based control where motor torque is provided based on an amount of torque applied by a driver; and second, calculating a reference driver torque and regulating handwheel torque that causes the EPS to achieve a desired torque. Further, steer by wire EPS system use both, the torque control mode and the position control mode.
Transitioning from one operating mode to another during driving the vehicle, thus leads to the EPS, transitioning from one operating mode to another. Typically, the EPS includes a separate module for each operating mode of the EPS. There are considerable variations in the EPS mechanical design in terms of motor inertia, hand wheel inertia, and stiffness in the system.
Accordingly, it is desirable to have objective, and uniform, control architecture of the EPS that operates regardless of the mechanical parameter variations and yet gives consistent results, irrespective of changes in the hardware. Such an objective architecture can lead to improvement of the EPS systems, because once the trade-offs for a particular EPS system are identified, those can directly be applied to another EPS system, reducing system dependent control tuning effort. Further, because the objective architecture works for all modes of operation of the EPS, controlling and tuning of the EPS can be simplified.